1. Field of the Invention
The present invention relates to an optical device module and a method for fabricating the same. Specifically, the present invention relates to an optical device module including a plurality of optical devices, flexible substrates connected to the optical devices, and electronic components mounted on the flexible substrates and to a method for fabricating the same.
2. Description of the Prior Art
In recent years, optical device modules have been developed in which an optical device having a light receiving/emitting function and a drive circuit for the optical device are integrated. Examples of such an optical device module include optical pickups used as for reading DVDs with the optical device and camera modules for mobile phones. There is a demand for these optical device modules to be downsized according to size reduction of built-in components.
More specifically, examples of the above optical device module are solid-state image sensors (image sensing modules) using as an optical device a solid-state image sensing device, such as a charge-coupled image sensing device (CCD), a static induction transistor image sensing device (SIT) or a charge modulation image sensing device (CMD). These solid-state image sensors are often built in compact camera units. These solid-state image sensors are used in a manner incorporated in a hardened tip of an insertion tube inserted in the compact camera unit. Such a compact camera unit is demanded to have a tip shorter and narrower in outer diameter because of use in archeological excavation, for search for narrow spaces in disasters and for internal investigation of artifacts. From this point of view, it is important how a solid-state image sensor is downsized. In addition, in order to release compact camera units at low price, it is also an important challenge to improve the assembly efficiency of solid-state image sensors and thereby save the production cost.
There is known a solid-state image sensor intended to attain size reduction and cost saving, wherein leads on a flexible substrate having an IC and a chip component mounted thereon are bent and connected to bumps on a particular edge of a solid-state image sensing device and the back surface of the IC is adhered to the back surface of the solid-state image sensing device (see, for example, Japanese Laid-Open Patent Publication No. 11-271646).
FIG. 14 is a conceptual cross-sectional view showing the structure of the known solid-state image sensor disclosed in the above document.
As shown in FIG. 14, first, a solid-state image sensing device 902, a semiconductor device (an IC chip) 903, a chip component 904 are mounted on a flexible substrate 901 and the flexible substrate 901 is connected to external signal lines 905. Thereafter, the flexible substrate 901 is bent at right angles at three locations so that the bottom surface of the solid-state image sensing device 902 and the top surface of the IC chip 903 are opposed to each other. Both the surfaces are adhered to each other by an adhesive 922. Then, the side surfaces of the chip component 904 are adhered to opposed parts of the bent substrate 901 by unshown adhesive. In this manner, a solid-state image sensor for an electronic endoscope is formed with a compact configuration. The above Japanese Laid-Open Patent Publication No. 11-271646 describes that since the solid-state image sensor is configured by bending the flexible substrate 901 in a rectangular shape and adhering the back surfaces of the IC chip 903 and the solid-state image sensing device 902 to each other, this provides size reduction and cost saving without deteriorating working efficiency.
There is also known another solid-state image sensor intended to attain size reduction, wherein a flexible substrate is bent in the shape of a box, electronic components are mounted on the flexible substrate inner surfaces of the box shape and a solid-state image sensing device is connected to terminals on the bottom of the flexible substrate (see, for example, Japanese Laid-Open Patent Publication No. 2000-210252). The Japanese Laid-Open Patent Publication No. 2000-210252 describes that since the flexible substrate is bent in the shape of a box all surfaces of which are rectangular and electronic components are mounted on the substrate inner surfaces of the box shape, the image sensing unit can be downsized, thereby narrowing and downsizing the endoscope tip.
Each of the two solid-state image sensors mentioned above includes one solid-state image-sensing device and can produce only monochrome images.
However, color images are required for archeological excavation, for search for narrow spaces in disasters and for internal investigation of artifacts. Moreover, it is required to mount an infrared light source or a laser light source for length measurement together with a solid-state image sensor. In such a case, it is necessary to mount a plurality of solid-state image sensing devices on one camera unit, and to mount a light source together. If the solid-state image sensors of Japanese Laid-Open Patent Publication Nos. 11-271646 and 2000-210252 including a plurality of solid-state image sensors are used, or a light emitting element is mounted together to form a camera unit, the size of the camera unit itself increases. This is because the plurality of image sensors are used although each image sensor is small. Moreover, it is very difficult to provide the solid-state image sensing devices in a lens-barrel accurately adjusting such that optical axes of the solid-state image sensing devices coincide with each other.
Japanese Laid-Open Patent Publication No. 56-98881 discloses a solid-state image sensor in which three solid-state image sensing devices are combined but provides no description as to a peripheral circuit for driving these solid-state image sensing devices. In an actual solid-state image sensor, it is necessary to integrally build in a lens-barrel the solid-state image sensing devices and a wiring substrate having the drive circuit mounted thereon. Japanese Laid-Open Patent Publication No. 11-271646 and Japanese Laid-Open Patent Publication No. 2000-210252 disclose a technique to make these integrated components compact. However, a technology to make a plurality of adjacent solid-state image sensing devices and a wiring substrate compact has not been disclosed.